Industry standard binders used for fibre insulation, for example glass wool and rock wool insulation are based on phenol formaldehyde. Whilst such binders can provide suitable properties to the insulating products there has for some time been a desire to move away from the use of phenol formaldehyde, particularly due to environmental considerations.
Traditional polyester based binder systems have previously been proposed but have not gained acceptance in the insulation industry, particularly as their strength in holding the mineral fibres together, especially when exposed to moisture or weathering, has been perceived as insufficient.
To date, only one low formaldehyde based mineral insulation binder system has been used on an industrial scale on glass wool insulation; this is based on polyacrylic acid and supplied by Rohm&Haas. Unfortunately, the highly acid nature of these types of binders can cause excessive corrosion of manufacturing plant unless significant investment is made in acid resistant equipment. U.S. Pat. No. 5,977,232 discloses a formaldehyde free binder for glass wool insulation based on a polycarboxylic acid. European patent application EP1698598A discloses use of a corrosion meter to try to mitigate problems associated with polycarboxylic acid-based fibreglass binder resins. In addition, whilst the strength of these binders is acceptable for some applications it is not as good as the commonly used phenol formaldehyde based binders.
It has not been thought possible to provide a formaldehyde free binder system useable on an industrial scale that will confer required characteristics, including strength, to mineral wool insulating products without encountering the difficulties associated with highly acidic liquid binder systems.